Lighting devices have been used in various applications, such as those for home use, industrial use, and commercial use, and developed with various light sources and structures in accordance with requirements of the applications. In such a lighting device, when a light source generates heat, it is necessary to take measures to deal with radiation of the heat so that the heat does not cause the lighting device to fail. As an example of those measures, a heat sink as a means of radiating heat is proposed to be installed to the lighting device.
In the conventional art, for example, a lighting fixture, which has a hollow cylindrical heat sink, is known. The lighting fixture has a socket to which a lamp is mounted, the hollow cylindrical heat sink, which surrounds the socket and is closed at one end. A heat transferring piece mounts the socket to an inner surface of the heat sink. The heat sink and the heat transferring piece are made of a metal that has high thermal conductivity. The heat sink has heat radiating fins around its outer circumference to radiate the heat of the lamp.
For another example, a lighting equipment, having a bracket to which a light source and a heat sink are fixed, is also known. The lighting equipment has a stage pivotally supported on a base and driven by an actuator. The stage is provided with a condenser lens such that a rear focal point of the lens is positioned on the pivot axis of the stage. The bracket is attached to the base. The light source, which is fixed to a surface of the bracket facing the lens, is positioned at the rear focal point of the lens. Light from the light source is transmitted through the lens. The heat sink is fixed on a surface of the bracket opposite to the surface of the bracket having the light source, to radiate the heat of the light source. A casing is attached to the bracket to enclose the heat sink.
Nevertheless, in such conventional lighting devices, even though measures for radiating heat of light sources by the use of heat sinks such as those described above have been proposed, there is still room for improvement. For example, in the above-described lighting fixture, the hollow cylindrical heat sink functions as a housing to support the light source and creates a closed space. In the above-described lighting equipment, the heat sink is fixed on the bracket which is attached to a casing to create a closed space to enclose the heat sink. Accordingly, in those conventional lighting devices, a sufficient radiating effect cannot be obtained for a high-power light source because the heat of the light source is adversely confined to the closed space.
Further, as in the above-described lighting fixture and equipment, because the light source and the heat sink in a conventional lighting device are both fixed directly or indirectly to a casing, a support bracket, a wall, a ceiling, or the like, an illumination angle of the light source cannot be effectively changed. If the illumination angle is to be changed, another member that can change the illumination angle must be further provided to the lighting device. Accordingly, those conventional lighting devices cannot be effectively made more compact in size.